The type of automobile lighting system that we are concerned with comprises: a light source that operates essentially continuously, an elongated light guide for transmitting light from the source to an output location spaced from the source, and a lens at the output location for receiving light from the light guide and transmitting such light to a location exterior to the automobile. The system also includes an indicating device that controls the light delivered to the lens, thereby providing a light signal that serves as an external indication to others of the driver's intentions or of the status or position of the automobile.
It is possible to use for the indicating device of such a system a solid-state in-line switch in the light guide for controlling the light passing therethrough, but such switches typically leave something to be desired in terms of efficiency and contrast ratio. We are concerned with providing an indicating device for use in such a system that is highly efficient and provides very high contrast ratio, i.e., the ratio of light output from the device when in an "on", or non-blocking, state to light output from the device when in an "off", or blocking, state.